Light emitting diodes are inorganic semiconductor devices that emit light, and have features such as eco-friendliness, low voltage, long lifespan, low price, and the like. Although light emitting diodes have generally been applied to lamps or devices for displaying simple information such as numerals, light emitting diodes have also recently been used in various fields including displays, automobile head lamps, projectors, and the like, with the development of technology, particularly, information display and semiconductor technologies.
Conventionally, a lateral light emitting diode (lateral LED) is fabricated by sequentially growing a plurality of semiconductor layers including an n-type semiconductor layer, an active layer and a p-type semiconductor layer on a growth substrate, followed by partially etching the p-type semiconductor layer and the active layer to form an n-type electrode and to form a p-type electrode on the p-type semiconductor layer.
In such a method, although the lateral light emitting diode can be relatively easily fabricated, such a light emitting diode has a reduced light emitting area due to removal of part of the active layer. In addition, the use of the growth substrate having low thermal conductivity, such as a sapphire substrate, results in increase in junction temperature due to heat generated by the light emitting diode, thereby causing deterioration in internal quantum efficiency.
To solve such problems of the lateral light emitting diode, a variety of vertical light emitting diodes have been developed. In vertical type light emitting diodes, since a sapphire substrate is removed by laser lift-off (LLO), it is possible to prevent deterioration in efficiency due to heat.
However, high intensity laser beams cannot be used in fabrication of vertical light emitting diodes since the semiconductor layer can suffer from cracking. Furthermore, when a substrate formed of the same material as that of a nitride semiconductor layer, for example, a gallium nitride substrate, is used as the growth substrate, it is difficult to use the laser lift-off process due to small difference in energy band gap between the gallium nitride substrate and the nitride semiconductor layer.